Chemical constituents in fluid streams are altered in many ways, including alteration by application of electrically generated plasmas. Most prior art devices relying on electrically generated plasmas including but not limited to electrostatic particle precipitators, electronic insect killers, and ozonizers, have low efficiencies. Chemical constituents are also altered in reactive beds wherein the beds have small particles that may be fixed or fluid, depending upon the flow rate of the stream, and may be batch or continuous. Fixed beds are those in which the particles are stationary and fluid flows in the interstices between the particles, and fluid beds are those in which the particles are agitated by buoyant forces of a flowing fluid. Depending upon particle size and fluid flow rate, the particles may be fluid or bubbling. When particles are fluid, the net gravitational and buoyant forces on the particles are equal, and there is no net force on the particles permitting them to move about chaotically in a flow stream. The chaotic motion enhances particle-to-particle contact and fluid mixing, as well as enhances heat transfer. When particles are bubbling, there is a net force in the direction of the buoyant force and are carried by the flow stream, causing separation of particles and reduced particle-to-particle contact. Batch reactors are loaded with a charge, then unloaded after processing. Continuous reactors receive an input stream and produce an output stream without needing to reload a charge. Throughout this specification, reactors and reactive beds are of the continuous reactor type.
Often the particles in a reactive bed are a catalytic material, or the particles are inert with an imposed electrical potential. Reactive beds are commonly used to treat contaminated fluids including gases or liquids; for example, air or water. Contaminants include but are not limited to organic compounds, sulfur compounds, and nitrogen compounds, including ammonia, and chlorinated and fluorinated compounds. Contaminated fluids are passed through and interact with the energized bed of particles and undergo chemical change. Chemical change may be a result of chemical or physical interaction of contaminants with the particles, or interaction with a plasma formed near the particles. Nevertheless, contaminants are decomposed into unharmful byproducts, which are then passed out of the reactive bed. Reactive beds are also used to produce useful products in chemical processing.
U.S. Pat. No. 4,954,320 to Birmingham, et al. describes a continuous flow reactive bed that utilizes an "active plasma" wherein the "active plasma" has "a higher energy state than possible with devices comprising the current art" for decomposing contaminant aerosols and gases along with ozone and phosgene. The "active plasma" is created by electricity having a frequency from 0.5 to 40 kHz. Physically, the Birmingham et al. reactive bed contains dielectric particles packed within a container with an imposed electrical potential with gases flowing through interstices between the particles. The particles are static or non-fluidized.
An article entitled THE DESTRUCTION OF VOLATILE ORGANIC COMPOUNDS BY AN INNOVATIVE CORONA TECHNOLOGY, by GH Ramsey, N Plaks, CA Vogel, and WH Ponder of the Air and Energy Engineering Research Laboratory, Environmental Protection Agency (EPA), Research Triangle Park, N.C., and LE Hamel of Acurex Corporation, discloses two corona discharge apparatus. The first is a pulsed corona-induced plasma chemical process that does not contain pellets or particles, and the second is a pelletized bed reactor requiring pellets of very high dielectric constant, for example barium titanate pellets with a dielectric constant of about 6000.
Another article entitled AN ELECTROSTATIC PRECIPITATOR USING PACKED FERROELECTRIC PELLET LAYER FOR DUST COLLECTION, by A Mizuno and H Ito from the Proceedings: Eighth Particulate Control Symposium, Vol. 1 Electrostatic Precipitators, EPRI GS-7050, Nov. 1990, discloses use of 60 Hz electricity to impress an electrical potential across a bed of packed pellets for removal of dust particles from air. In addition to "electrifying" the packed pellets, a direct current corona discharge is used to precharge dust particles prior to their contact with the packed pellets. The article further discloses that, consistent with Ramsey et al., high dielectric pellets are preferred, specifically ferroelectric pellets having dielectric constants greater than 33.
It would be advantageous to achieve the benefits of a reactive bed using lower frequency electricity and most advantageous to use standard 50 to 60 cycle electricity. Further advantages would be realized by using low cost, low dielectric pellets or particles.
The present invention relates to an improved reactive bed and methods for chemically altering fluids.